1. Field of the Invention
The present invention relates to an image forming apparatus capable of performing double-sided printing.
2. Description of the Related Art
There is an image forming apparatus which is provided with a circulating transfer path including a sheet reversing path and is capable of executing both of single-sided printing and double-sided printing. When single-sided printing is selected, the image forming apparatus of this type performs the single-sided printing by making printing on one of surfaces of a recording medium and then discharging the printed recording medium without using the sheet reversing path. On the other hand, when double-sided printing is selected, the image forming apparatus performs the double-sided printing by making printing on one of surfaces of a recording medium, then reversing the recording medium having the one surface already printed, by transferring the recording medium on the circulating transfer path, and then making printing on the other surface of the recording medium.
Japanese Patent No. 3880281 discloses an image forming apparatus including: a first detector configured to detect a sheet re-feed waiting state of a recording medium being transferred along a circulating path; a second detector configured to detect the sheet feed waiting states of a sheet for double-sided image formation and of a sheet for single-sided image formation by using a sheet feeder; a determination unit configured to determine, based on results of detection by the first detector and the second detector, whether or not a sheet for double-sided image formation is included within a feed waiting sheet range including twice as many sheets as the sheets from the first feed-waiting sheet to a re-feed waiting sheet for double-sided image formation; and a controller configured to treat the first feed waiting sheet as a sheet for double-sided image formation when the sheet for double-sided image formation is included in the feed waiting sheet range, and to thus perform control to re-feed the first feed waiting sheet along the circulating path.
The image forming apparatus disclosed in Japanese Patent No. 3880281 detects whether or not a sheet for double-sided image formation is included in the feed waiting sheet range including twice as many sheets as the sheets from the first feed-waiting sheet to a re-feed waiting sheet for double-sided image formation, treat the first feed waiting sheet as a sheet for double-sided image formation when the sheet for double-sided image formation is included in the feed waiting sheet range, and thus perform control to re-feed the first feed waiting sheet along the circulating path. In this way, the image forming apparatus is able to reduce processing time required for image formation including both of double-sided image formation and single-sided image formation, and thereby to prevent a decrease in productivity of image formation including both of the double-sided image formation and the single-sided image formation.